[R] Add a vector to the values in a specific dimension of an array

[Bill.Venables at csiro.au]

It depends on how big A is and how much memory you have.  Here is one lazy way.

A <- aperm(aperm(A, c(2,1,3,4)) + x, c(2,1,3,4))

Bill Venables

-----Original Message-----
From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf Of huron
Sent: Thursday, 19 May 2011 1:47 PM
To: r-help at r-project.org
Subject: [R] Add a vector to the values in a specific dimension of an array

Hello,

A simple question, although I can't find an answer via my google/forum
search:

I have a 4-dimensional array; call it A[1:M,1:N,1:P,1:Q]. I have a vector x
that is N by 1.  

I would like to "quickly" add x to the 2nd dimension of A; in other words, I
want a quicker way of doing the following:

for (m in 1:M) {
  for (p in 1:P) {
    for (q in 1:Q) {
      A[m,,p,q] = A[m,,p,q] + x
    }
  }
}

Thanks in advance!

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